1. Field of the Invention
The present invention relates generally to photolithography. More specifically, systems and methods for gray scale lithography for defining edges such as on microelectronic device patterns during integrated circuit fabrication are disclosed.
2. Description of Related Art
Conventional reticle writing systems create and move edges by modulating pixel strengths on and mainly outside of an edge with partial pixel intensities, i.e., gray levels (GLs). As a feature becomes smaller, the two edges of one-dimensional features interfere with each other to cause undersized features with non-linear degradation in size and slope. As the design feature becomes smaller, conventional methods of exposing small features results in a diminishing CD size when compared to the design CD size. The problem is exacerbated in that uniformity or variability of the critical dimension (CD) is also degraded and, when convolved with process constraints, yield is severely limited. Critical dimension (CD) generally refers herein to the width of a patterned line or the distance between two lines of the sub-micron sized circuits in a chip.
Thus, it is desirable to improve upon reticle writing systems that create and move edges by modulating pixel strengths with GLs so that the reticle writing system can write smaller features with increased CD fidelity, improved CD uniformity, and improved edge slope.